Prefabricated set for making a cooking surface

ABSTRACT

A prefabricated set for making a cooking top. The prefabricated set includes a glass ceramic hot plate and a frame including a part extending at the hot plate periphery and another part extending in a plane substantially vertical to the hot plate. At least one of the two frame parts includes an elastomer over-molding. A cooking top can be manufactured including such a prefabricated set.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The invention relates to a prefabricated assembly, intended for theproduction of cooking tops, comprising a glass-ceramic plate or hob.

2. Discussion of the Background

Such cooking tops may include, inter alia, heating elements, such asradiant or halogen hotplates, and regulating means for varying the powerof the latter.

These various elements are usually placed in a metallic structure calleda “box” and are covered with a glass-ceramic plate equipped with a metalframe which encloses the structure.

The fitting of these cooking tops is completed by placing theglass-ceramic plate on the metal structure. Beforehand, theglass-ceramic plate and the frame are joined together by bonding using asilicone adhesive, which is suitable for such a use. This is because thesilicone adhesive fulfils functions of different and complementarytypes.

Firstly, it allows the glass-ceramic plate to be held on the frame in adefined position; a cooking top thus produced may be easily transported,all the elements of which it is composed being fastened together, afterfitting onto the box.

Another function of the silicone adhesive is to seal between the metalframe and the glass-ceramic plate.

The subassembly formed by the plate and the frame must, on the one hand,be well sealed so that water, for example the water used for cleaningthe visible surface of the glass-ceramic plate, cannot penetrate insideand risk creating a short circuit. On the other hand, from a hygienestandpoint, since such a plate is used for the preparation of food, itis necessary to avoid any risk of fouling in the areas difficult to getat and impossible to clean, in order to prevent the development ofgerms.

Another function again fulfilled by the silicone adhesive is to dampenmechanical shocks. It thus prevents direct contact between the metalframe and the glass-ceramic plate and it can also compensate forexpansions of the metal frame, the glass-ceramic hob having a virtuallyzero expansion coefficient. Another advantageous characteristic of thesilicone adhesive is that it has good temperature resistance. Althoughthe silicone adhesive is used only in the peripheral part of theglass-ceramic plate, and therefore at a certain distance from theheating areas, this temperature resistance must be high.

Thus, the periphery of the plate nevertheless undergoes a temperaturerise when one or more hotplates are in operation. In addition, a heatedvessel, such as a saucepan, may be placed on the edge of the plate andtherefore exposes the frame to a high temperature.

A final function of the silicone adhesive is an aesthetic one: since atleast part of the adhesive is deposited via the top, it is important tobe able to smooth it so as to give it an attractive appearance since atleast part may remain visible.

On the other hand, the fitting operation, consisting in bonding theglass-ceramic plate to the metal frame using an adhesive of the typementioned above has several drawbacks.

In the first case, since the amount of adhesive needed is relativelylarge, the cost of this product is relatively high. Another drawback isdue to the curing time which increases with the amount of material,thereby leading to an increase in the manufacturing costs.

Finally, another drawback arises during the actual fitting. This isbecause glass-ceramic plates are usually delivered as they are tocooking-top manufacturers who are responsible for the assembly. Apriori, such a factory assembly does not present insurmountable problemsinsofar as the operators do have the necessary tools. On the other hand,such assembly is much more difficult for an artisan who has to refit aglass-ceramic plate into a metal frame after an electrical-type repairhas been made or else has to change this plate which may have beendamaged. This is because it appears to be difficult for the artisan tofasten the glass-ceramic plate since he must both place the siliconeadhesive around the periphery of the plate on the internal face andalong the edges, smooth the adhesive in the visible area and keep theplate well centered, while pressing it during the above operations andduring the time for curing the adhesive, which is relatively long, asmentioned above.

The removal of such a glass-ceramic plate is also not easy. The artisanmust cut the silicone adhesive from below, that is to say on the lowerface side of the glass-ceramic plate, and cut it from above, that is tosay along the edge of the plate. These two operations, which must becarried out over the entire periphery, are not simple as the two cuttinglines must meet in order to separate the two elements—the glass-ceramicplate and the metal frame. In addition, and more particularly whencutting on the internal face side of the glass-ceramic plate, it is noteasy to make this cut without incurring the risk of scratching the lowerface of the plate, which is the most fragile face of the plate.

This risk of scratching may lead to a risk of stress cracking andtherefore to fracture of the plate. Removal of a glass-ceramic plate,for the purpose of refitting it later, therefore appears to beimpossible or almost impossible to accomplish without damaging theplate.

Moreover, in order to refasten it to the frame, it is necessary toremove as far as possible all traces of silicone adhesive from theprevious fitting, something which also incurs the risk of causingscratches, with the same consequences as before.

To remedy these drawbacks, it has already been proposed according topatent FR 2,744,201 to provide the glass-ceramic plate with athermosetting profile overmolded around the lower peripheral part, whichprofile, by the use of suitable fastening means, allows the plate to befastened to a metal frame without direct contact between the two.

It has also been proposed, especially in EP 0,449,347, to directlyovermold, by a twin-shot injection molding technique, a plastic framearound the periphery of the glass-ceramic plate, the plastic frame thenbeing fastened to a metal base, supporting the various heating elements.

This solution is not entirely satisfactory. Since the plastic frame isdirectly in contact with the upper part of the worksurface, theinterface between these two parts is not sharply defined, particularlyfrom a sealing standpoint. Consequently, the risk of fouling isconsiderable.

SUMMARY OF THE INVENTION

The inventors were therefore faced with the task of providing aprefabricated assembly of the type mentioned above, that is to saycomprising a glass-ceramic hob and a frame, which makes it possible,once fitted into the cooking top, for the latter to have a very sharplydefined interface with the worksurface for which it is intended.

To do this, the subject of the invention is a prefabricated assembly,intended for the production of a cooking top, comprising a glass-ceramicplate or hob and a frame consisting of a part extending around theperiphery of the plate and of another part extending in a planeapproximately vertical to the plate, wherein at least one of the twoparts of the frame includes an overmolding made of an elastomer.

This is because the overmolding in the outer peripheral part of theframe makes it possible to ensure that there is a very well definedinterface with the upper part of the worksurface, particularly from asealing standpoint. This is because the elastic nature of the elastomerallows the profile to follow the shape of the worksurface as closely aspossible, which may prove to be effective, particularly when the latteris not strictly plumb and/or when its surface finish is not uniform.

The frame according to the invention is preferably made of plastic.Advantageously, it is molded. Again preferably, it is made of a polymerresin resistant to temperatures of at least 180° C.

With regard to the connection between the glass-ceramic hob and theframe, it may be chosen to overmold the frame directly onto the hobinstead of joining them together by a seal made of an elastomer.

Such a choice may be made especially according to the geometry of themanufacturing technique inherent in the frame.

In order to integrate the controls for the heating elements, otherheating means such as gas burners and/or other functional elements forthe glass-ceramic plate, such as a clock, the frame advantageously hasemerging holes through which elastomer knobs are overmolded.

According to a very advantageous characteristic of the invention, theovermolding is a profile.

According to this same characteristic, each of the two aforementionedparts of the frame advantageously includes an elastomer profile.

Very advantageously, the elastomer profile of that part of the framewhich extends in the approximately vertical plane of the plate consistsof tabs, preferably having grooves. The flexible “tabs” of theovermolded profile make it possible, according to this embodiment, toperfectly immobilize the cooking top in the worksurface, even if thecutting of the latter has not been carried out to the desiredtolerances. In this way, it is possible to avoid leaving a large gapbetween the vertical walls of the frame and the worksurface, which gapcannot be compensated for in this case solely by the presence of wedgingpieces difficult to fit.

Another advantage provided by this embodiment of the invention is theguarantee of not damaging the worksurface when fitting the assembledcooking top into the latter.

The elastomer profile of that part of the frame which extends around theperiphery of the plate preferably has a lip, thereby making it possibleto avoid even further the risk of fouling.

Because of its elasticity, this lip, together with the aforementionedflexible retention elements, participates in pressing the frame onto theworksurface.

The elastomer of the overmolding according to the invention isadvantageously a silicone.

The invention also relates to a cooking top incorporating aprefabricated assembly defined above, the frame of which is fastened toa base supporting heating elements, such as radiant or halogen elementsand/or at least one atmospheric-gas burner and/or at least one inductionheating means.

Finally, the invention relates to a process for manufacturing aprefabricated assembly according to the invention. According to thisprocess, the following steps are carried out:

a) a molded frame is introduced into a punch of shape such that it ispossible to inject an elastomer at the surface of at least one of thetwo parts of the frame;

b) a glass-ceramic hob is placed in the punch, slightly above the moldedframe;

c) the assembly thus formed is closed by means of a die of shape atleast partly complementary to the punch;

d) an elastomer is injected into the channels formed by the gap betweenthe punch and the die;

e) the elastomer is cured; and then

f) the assembly thus formed is ejected.

The advantages afforded by the invention are numerous. Firstly, sincethe elastomer is injected and then cured, it no longer has to besmoothed by hand, as could be the case according to the prior art, itssurface finish no longer impairing the decorative appearance. Likewise,by injecting the elastomer onto a frame already formed, it is possibleto use frames of varied shapes and/or colours. Such varieties contributeto the aesthetic appearance of the cooking top.

The varied shapes also make it possible to integrate into the frameitems of equipment usually integrated into the plate, such as themembers for controlling the heating elements, which usually require theplate to be extremely carefully drilled.

For reasons of manufacturing costs, the frame used according to theprocess of the invention is preferably made of plastic.

The elastomer used is advantageously silicone.

According to a very advantageous characteristic of the process,high-frequency curing is carried out in step e).

The fact of curing the elastomer according to the invention at highfrequency also makes it possible to save a considerable amount of timein manufacture. In addition, in such a process, the tooling used is thatnormally used for an elastomer. Thus, the flexible contact between thetooling, particularly the mould, and the various parts forming theprefabricated assembly according to the invention incurs no risk ofdegrading the materials, especially the glass ceramic of which the hobis composed.

Thus, in industrial production the risk of scrap is reduced.

BRIEF DESCRIPTION OF THE DRAWINGS

Further details and advantageous characteristics will emerge below onreading detailed examples according to the invention, with reference toFIGS. 1 to 2 e which represent, respectively:

FIG. 1: a cooking top incorporating a first prefabricated assemblyaccording to the invention and placed in a worksurface;

FIGS. 2a to 2 e: the various steps in the process for manufacturing asecond prefabricated assembly according to the invention.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

FIG. 1 is a sectional view showing a cooking top 1, made according tothe invention, integrated into a worksurface 2 of a kitchen.

This cooking top 1 is essentially composed of a glass-ceramic plate orhob 3 and of a prefabricated assembly 4 according to the invention whichis fastened to a metal base 5, of rectangular cross section, by means ofscrews (not shown).

Heating elements (not shown) are fastened, in a manner known per se, tothis base 5.

The combination of the prefabricated assembly according to the inventionand the metal base therefore substitutes, at least from the standpointof the enclosure function, for a metal frame used according to the priorart. A frame 6 made of a plastic, especially one filled with glassfibres, possibly like the plastics mentioned below, constitutes thesupport for the prefabricated assembly according to the invention.

This frame 6 essentially comprises three parts, namely the vertical sidewalls 61, 62, the outer peripheral part 63 which surrounds theglass-ceramic hob 3, being directly in contact with it, and a plane part64 which extends approximately in the main plane of the glass-ceramichob 3.

This plane part 64 has apertures, the function of which will beexplained below.

Extending around the entire periphery of the frame 6 is a siliconeprofile 7. This has the shape of a lip 71 for the part directly incontact with the upper part of the worksurface. This lip 71 has thefunction of ensuring a very clearly defined interface between the frame6 and the upper part of the worksurface, that is to say, inter alia, toensure sealing with respect to liquids and with respect to food likelyto be nearby.

Moreover, the curved shape of the lip 71 gives it an aestheticappearance.

The silicone profile 7 has, in a vertical part thereof, tabs 72, 73 incontact, on the one hand, with the entire height of the vertical sidewalls 61, 62 of the frame 6 and, on the other hand, with the entireheight of the worksurface. The elastic nature of the silicone makes itpossible for these tabs 72, 73 to be deformed when inserting the cookingtop into the worksurface and therefore to ensure that these two elementsare completely immobilized, with a gap being formed between them.

Removal of the cooking top is also very easy, without running the riskof damaging the frame 6 and/or the worksurface 2.

As regards the plane part 64 of the frame, this has two circularapertures 65 and one rectangular aperture 66.

Through the two circular apertures 65 are snap-fastened, or preferablyovermolded onto the frame, silicone control knobs 67 which, once theyhave been pushed in, make it possible to operate the heating members(not shown).

Placed below the rectangular aperture 66 is a digital-type display whichmakes it possible to display the time and/or programmed duration of aheating cycle of at least one of the heating members. It may alsoindicate which heating member is in operation if the hob is powered, thetemperature of the heating member(s) etc.

Finally, under this plane part, opposite the apertures described, isencapsulated, using silicone, a substrate 68 on which conducting tracksare etched, the electrical supply to the various members beingestablished via these conducting tracks.

FIGS. 2a and 2 e show the various successive steps in the process formanufacturing a second refabricated assembly according to the invention.

According to this second embodiment, the prefabricated assembly 4 andthe glass-ceramic hob 3 are joined together via a silicone seal 8.

FIG. 2a relates to the initial step of placing a molded frame 6 in apunch 9. This molded frame 6 has a similar shape and chemical nature asthat in FIG. 1.

FIG. 2b shows the glass-ceramic plate 3 placed in the punch 9, so as tobe slightly above the frame 6, leaving a gap 10.

Once the two aforementioned parts have been placed in the punch 9, a die11 is applied against the punch 9 and, at certain places, against theplate 3 and the frame 6 in such a way that closed injection channels 12are created, as shown in FIG. 2c.

Silicone is then injected into these channels 12 by means of a suitabledevice.

Once the channels 12 have been completely filled with silicone material(as shown in FIG. 2d), the injection is stopped and this same materialis then cured using a high-frequency technique lasting for a time of 0.5to 2 minutes, depending on the mass of silicone to be converted.

The die 11 is then released from the punch 9 and the prefabricatedassembly is ejected, as shown in FIG. 2e.

Such a process has the advantage of being simple and quick to carry out.It is also advantageous insofar as new series, with new types of moldedframe, may be easily produced without any additional production cost, itbeing easy to produce new die and/or punch tooling.

It goes without saying that many modifications may be made withoutthereby departing from the scope of the invention. Thus, any new plasticfor the molded frame may be suitable as long as it withstands hightemperatures, typically greater than 250° C.

Thus, for example, the plastic of the frame according to the inventionmay be chosen from polytbutyl terephthalate (PBT), polyphenylenesulphide (PPS), polyetheretherketone (PEEK), polyacrylate (PAR),polyethersulphone (PES), polyetherimide (PEI), polyamideimide (PAI),liquid-crystal polymer (LCP), polytetrafluoroethylene (PTFE),polyetherethersulphone (PEES), polyepoxides (EP) and, possibly,polysulphone (PSF), fluoropolymer resins (FEP, such as, for example,PTEFE, PFA, ETFE, etc.), polythioethersulphone (PTES), thermoplasticpolyimide (TPI), crosslinked polyimide (CLPI), polyetherketone (PEK),polyethernitrile (PEN), polycyclohexylene terephthalate (PCT) andpolyphthalamide (PPA).

For material cost reasons, the frame may advantageously be chosen frompolyester resins (UP).

Likewise, any other equivalent profile able to be injection-moldedaccording to the invention falls within the scope of the invention aslong as the analogous characteristics with regard to silicone, such aselasticity and resistance to high temperature, are fulfilled.

The elastomers sold respectively under the names VITON and KALREZ byDuPont de Nemours are thus perfectly suitable.

Likewise, the elastomers sold under the brand names FLUOREL and CHEMRAZby 3M and Green Twin, respectively, are perfectly suitable.

What is claimed is:
 1. Prefabricated assembly, for the production of acooking top for fitting on a worksurface, comprising: a glass-ceramicplate or hob and a frame comprising a first part extending around theperiphery of the plate and a second part extending in a planeapproximately vertical to the plate, wherein at least one of the firstand second parts of the frame includes an overmolding made of anelastomer, said overmolding having a deformable tab which fills a gapformed between the frame and the worksurface for immobilizing the framewith respect to the worksurface.
 2. Assembly according to claim 1,wherein the frame is made of plastic.
 3. Assembly according to claim 1,wherein the frame is molded.
 4. Assembly according to claim 2, whereinthe frame is made of a polymer resin resistant to temperatures of atleast 180° C.
 5. Assembly according to claim 1, wherein the plasticframe is directly overmolded onto the glass-ceramic hob.
 6. Assemblyaccording to claim 1, wherein the frame and the glass-ceramic hob arejoined together by a seal made of an elastomer, of a silicone type. 7.Assembly according to claim 1, wherein the frame has holes formedtherein through which elastomer knobs are overmolded.
 8. Assemblyaccording to claim 1, wherein the overmolding is a profile.
 9. Assemblyaccording to claim 8, wherein each of the two parts of the frameincludes an elastomer profile.
 10. Assembly according to claim 8,wherein the elastomer profile of a part of the frame which extends in aplane approximately vertical to the plate comprises tabs having groovesformed therein.
 11. Assembly according to claim 8, wherein the elastomerprofile of a part of the frame which extends around the periphery of theplate has a lip.
 12. Assembly according to claim 1, wherein theelastomer of the overmolding comprises a silicone elastomer.
 13. Aprefabricated assembly as claimed in claim 1, said overmolding having acurved lip for sealingly contacting an upper part of the worksurface onwhich the frame is mountable.
 14. A cooking top incorporating aprefabricated assembly, which comprise: a glass-ceramic plate or hob anda frame comprising a part extending around the periphery of the plateand another part extending in a plane approximately vertical to theplate, wherein at least one of the two parts of the frame includes anovermolding made of an elastomer, said overmolding having a deformabletab which fills a gap formed between the frame and the worksurface toimmobilize the frame with respect to the worksurface, the frame beingfastened to a base for supporting heating elements, the elementscomprising at least one of a radiant element, a halogen element, atleast one atmospheric-gas burner or at least one induction heatingmeans.
 15. Process for manufacturing a prefabricated assembly, intendedfor the production of cooking tops for mounting on a worksurface, theassembly comprising a glass-ceramic hob and a frame having a first partextending around the periphery of the plate and a second part extendingin a plane approximately vertical to the plate, at least one of theparts including an overmolding having a deformable tab for filling a gapbetween the frame and the work station, which comprises: a) introducinga molded frame into a punch for subsequently injecting an elastomer at asurface portion of at least one of the first and second parts of theframe; b) placing the glass-ceramic hob in the punch so as to bepositioned slightly above the molded frame; c) closing the assembly thusformed by means of a die of a shape at least partly complementary to thepunch; d) injecting an elastomer into the channels formed by the gapbetween the punch and the die; e) curing the elastomer; and then f)ejecting the assembly thus formed.
 16. Process according to claim 15,wherein the frame comprises plastic.
 17. Process according to claim 15,wherein the elastomer comprises silicone.
 18. Process according to claim16, which comprises high-frequency curing which is carried out duringcuring of the elastomer.
 19. Prefabricated assembly for the productionof a cooking top, comprising: a glass-ceramic plate or hob and a framecomprising a first part extending around the periphery of the plate anda second part extending in a plane approximately vertical to the plate,wherein at least one of the first and second parts of the frame includesan overmolding made of a silicone type elastomer cured athigh-frequency.
 20. A cooking top incorporating a prefabricatedassembly, which comprises: a glass-ceramic plate or hob and a framecomprising a part extending around the periphery of the plate andanother part extending in a plane approximately vertical to the plate,wherein at least one of two parts of the frame includes an overmoldingmade of a silicone type elastomer cured at high-frequency, the framebeing fastened to a base for supporting heating elements, the elementscomprising at least one of a radiant element, a halogen element, anatmospheric-gas burner or an induction heating means.
 21. Process formanufacturing a prefabricated assembly for the production of cookingtops comprising a glass-ceramic hob and a frame having a first partextending around the periphery of the plate and a second part extendingin a plane approximately vertical to the plate, which comprises: (a)introducing a molded frame into a punch for subsequently injecting anelastomer at a surface portion of at least one of the first and secondparts of the frame; (b) placing the glass-ceramic hob in the punch so asto be positioned slightly above the molded frame; (c) closing theassembly thus formed by means of a die of a shape at least partlycomplementary to the punch; (d) injecting a silicone type elastomer intothe channels formed by the gap between the punch and the die; (e) curingthe silicone type elastomer at high frequency; and then (f) ejecting theassembly thus formed.